Doctor means for drying cylinders and calender rolls in paper making machines



Aug. 2, 1955 H. c. QVARNSTROM 2,714,219

DOCTOR MEANS FOR DRYING CYLINDERS AND CALENDER ROLLS IN PAPER MAKING MACHINES Filed Sept. 20, 1951 United States Patent DOCTOR MEANS FOR DRYING CYLINDERS AND ROLLS IN PAPER MAKING MA- Helle Cesar Qvarnstrdm, Stockholm, Sweden, 'assignor to Aktiebolaget Kafab, Stockholm, Sweden, a company of Sweden Application September 20,1951, Serial No. 247,417 8 Claims. (Cl. IS-256.5)

This invention relates to a cleaning or doctor arrangement for drying cylinders (driers), notably M. G. cylinders (glazing calenders), in paper making machines and the main object .of the invention is to provide means for keeping the cylinders entirely free from residual fibre particles and otherimpurities deposited thereon when the paper web is continuously passing over them so that the detrimental effect on the quality of the paper, particularly in the formation of indentations and inequalities in the paper surface, otherwise caused by said fibre particles and impurities is obviated.

Doctor means consisting of blades or knives of metal or in some cases scrapers of felt or rubber which are pressed against the surface of the drying cylinders and calender rolls have hitherto been used for this purpose. For a long time it was assumed that these known doctors kept the cylinders clean in a satisfactory manner because 'the cylinders were usually made of cast iron and .presented a greyish surface against which residual fibre particles etc. were not so easily visible under normal working conditions. After the introduction of cylinders with a nickel-plated surface, however, it was found that the cleaning capacity of these known doctors was extremely unsatisfactory, and investigations have shown that this is also the case when using cast iron cylinders, though residual particles first became visible to the naked eye against the smooth mirrorlike 'nickel'plated surface of the modern cylinders.

In view of the foregoing, the present invention has for its object to provide a roll doctor for drying cylinders and calender rolls in paper making machines, which "is arranged to bepressed against the surface of the cylinder and to be driven at a peripheral speed differing from that of the drying cylinder, thus continually producing a rubbing action between the surface of the roll doctor and the cylinder surface, whereby fibre particles and impurities deposited 'on the cylinder surface are effectively removed therefrom.

A furtherobject of the invention is to provide a felt roll-doctor for the purpose described adapted to exercise 'acleanin'g or polishing action on the surface of thedrying cylinder and at the same time preferably being so constructed as to be self-cleaning.

These and other objects 'of the invention will become apparent from the following description of a preferred embodiment of the invention which by way of example is schematically illustrated in the accompanying drawing. Preferablythe invention is intended to be applied in conmotion with paper machines of the so-called yankee type, but it is of course by no means 'restrietedhereto. In the drawing:

Fig.1 is a sectional elevation of a part of a paper making machine with a drying cylinder and a felt roll doctor according to the invention,

Fig. 2 shows-the part of the paper making machine in Fig. l viewed from the left,

Fig. 3'illustra'tes 'a doctor roller in partialaxial section and on an enlarged scale,

Fig. 4 shows across section of the doctor roller from the right in Fig. 3, and

Fig. 5 is an enlarged plan view of the driving arrangement at the righthand end of the doctor roller in Fig. 2.

The part of the paper making machine shown comprises a frame 1 and a drying drum 2, the latter being adapted to rotate to feed the paper in a manner known per se.

The other cylinders or drums of the paper making machine have been omitted in the figures for the sake of clarity, since they are not affected by the invention,

About a shaft 3 which is parallel to the drum 2 and supported by two parallel, upwardly directed lever arms 4 adapted 'to pivot in the plane of the shaft 3, a doctor roller 5 is arranged to rotate. The arms 4 are pivotally mounted at their lower ends on pivot pins 6 which are perpendicular to the shaft 3 and each of which is carried by a supporting member 7 which in its turn is adapted to pivot around an auxiliary shaft '8. which is parallel to the shaft 3, the supporting members 7 being provided with lever arms 9 which at their respective outer ends .are fitted with adjusting screws 10, springs or the like permitting adjustment of .the lever arms 9 in relation to the frame 1 of the paper making machine. By means of said lever system including the arms 4., the pivotpins 6, the supporting members .7 and the "lever arms 9 said adjustment is transferred to the felt roller causing it to press against the surface of the drying drum along the whole length thereof with adjustable pressure.

The arms 4 are provided at their upper ends '4' with spherical bearings 11 for the shaft 3 whereby ,theroller 5 may reciprocate or oscillate in an axial direction. During such movement the roller 5 will, of course, also move relatively to the drying cylinder 2 so that every point on the roller will be caused to rub against different viewed parts of the drying cylinders surface. .By this means any inequalities in the roller which might affect the 'latters cleaning capacity are counteracted while at the same time 'it is possible to employ a roller of atype to be described later, in which the heat of friction is rapidly dissipated and a self-cleaning effect 'is also obtained for. the roller.

The roller 5 is caused to rotate by a motor 12 and .a gearbox 13'which enables the rollers speed of rotation .to be regulated and its direction of rotation to be'reversed, if necessary. It has been found preferable in most cases to allow the roller 5 to rotate in the same direction as the drying cylinder .2, whereby the surfaces of "the roller and cylinder move against one another, as indicated by the arrows in Fig. '1, but in certain instances an improved 1 cleaningeifect may "be obtained when the roller rotates in the opposite direction, Between the gearbox 13 and the roller shaft 3 a'V-belt transmission 14 is arranged. in the present casethe motor 12 and gearbox 13 are mounted on a "bracket 15 .at one of the arms 4, 'andtherefore the shaft 3 is provided outside the spherical bearing 'at the upper end 4' of the arms 4 with universal joints "16 and the end of the shaft 3 nearest to. the transmission 14 is rigidly'mounted in'a member 17 projecting fromthe arm 4 so that the rotation can be'transmitted from the motor .112 to the roller 5 independently of the lattersreciprocating movements in the axial direction, and consequently, of transitional movements outside the spherical bearing of the shaft 3. The roller 5 may, of course, be'driven by other means than'those'shown andthe detailed construction of the driving device is not an essential ,part of the invention, but according to the latter, the roller-5 must be driven in some other 'way than by its direct peripheral engagement with the drying cylinder to enable "it to be'run at .a peripheral 'speed differing from that of the drying cylinder.

The reciprocating movement of the roller *5, which is controlled by thearms 4 adaptedtopivotin'theaxialplane of the =roller, is'-produced byconnectir'rg the "shaft Soothe 3 outside of the spherical bearing located at the upper end 4 of the arm 4, to the input shaft 19 of a wormgear 20 by means of two universal joints similar to those described With relation to the drive, the output shaft 21 of the said gear supporting an eccentric disc 22 around which one end of a connecting rod 23 is mounted, its other end pivoting round a pin 24 or the like which is rigidly fixed to the machine frame. The wormgear 24) may be changed so that the speed of the rollers reciprocating movement, produced by the eccentric 22 and connecting rod 23 and forcibly controlled by the rotation of the wormgear, may be adjusted as required. The amplitude of the reciprocating movement may, of course, also 'be regulated by changing the eccentric disc 22 and also the connecting rod 23, if necessary. The Wormgear 20 is mounted'on a bracket 25 supported by the arm 4.

In effect the lever arms 4 and 9 form two bell crank levers pivotally mounted on either end of auxiliary shaft 8, each being swingable in a plane perpendicular to the shaft, their upstanding lever arms 4 being pivoted at 6 adjacent their mountings 7 so that roller 5 can be oscillated in an axial plane.

Should it be found preferable to employ similar means suspended downwards, in place of the upwardly directed arms 4, this will not in any way alter the constructional principle and method of operation of the device as will be readily understood.

The roller 5 is preferably constructed in the manner indicated in Fig. 3, where it consists of a plurality of spaced-parallel, flexible circular discs 26 of felt of wool or other material of organic or inorganic nature suitable for cleaning the drying cylinder, said discs 26 being threaded onto the shaft 3 and separated by intermediate discs or washers 27 of cardboard, felt, canvas, rockwool or other suitable material. The intermediate discs 27 have a smaller external diameter than the felt discs 26 so that the felt discs are peripherally separated and form an annular, ribbed, resilient, self-cleaning surface adapted to exercise a cleaning and polishing action on the surface of the drying cylinder to be cleaned When the felt roller is pressed against it, and furthermore, the intermediate discs are constructed in star-shaped form as toothed rings with the teeth directed outwards, whereby improved support and resilience is obtained in the felt discs 26 of the roller 5. The intermediate discs prevent the doctor roller when rubbing against the drying cylinder from being overheated and burned at its periphery while at the same time the particles scraped from the cylinder by the roller are more easily detached and the roller becomes self-cleaning. With this type of roller, however, an axial reciprocating movement is practically essential to prevent the formation of stripes or uncleaned strips on the drying cylinder 2 between the felt discs 26, and the stroke of the reciprocating roller must be greater than the total thickness of a felt disc and an intermediate disc. In order to prevent the felt discs as well as the intermediate discs from slipping on the shaft 3, the shaft is provided with a longitudinal spline 28 which serves as a locking member for a number of supporting discs 29 pushed onto the shaft 3, only one such disc being shown in Fig. 3 at one end of the roller 5; several of these discs should, however, be employed distributed along the length of the roller. The supporting discs 29, similarly to the felt and intermediate discs, are provided with a series of holes to receive a number of bars 30 running along the entire length of the roller. These bars are fixed in the two outermost supporting discs 29 at the respective ends of the roller and hold the parts of the roller together and at the same time they assist in preventing the felt discs from turning on the shaft 3.

When the roller 5 rotates in the same direction as the drying cylinder it has been found preferable to allow it to run at a peripheral speed which is substantially double of that of the drying cylinder. Thus, if the peripheral speed of the drying cylinder lies between 20 and 100 m./min., the peripheral speed of the doctor'roller should 4 at least be adjustable between the limits 50200 m./min.

It is obvious that in the device and arrangement described above all such alterations and modifications may be made as will fall Within the scope of the invention.

I claim:

1. A doctor arrangement for cleaning the drying and calendering rolls of a paper machine which comprises in combination, a rotatable roller the axis of which is parallel to that of the calender roll to be cleaned, means for pressing said roller against the periphery of said calender roll, means for rotating said roller with a peripheral speed independent of that of said calender roll, and means for imparting an axially reciprocating movement to said roller in dependence on the rotational movement thereof, said roller comprising a plurality of spaced parallel felt discs peripherally separated and providing an annular, ribbed, resilient, self-cleaning surface adapted to exercise a cleaning and polishing action on the calender roll surface when rotated and reciprocated.

2. A doctor arrangement as claimed in claim 1, wherein said roller comprises a shaft, a number of annular discs of a resilient fibrous material threaded on said shaft and a number of intermediate spacing washers between said annular discs, said washers having an outer diameter smaller than that of said discs and being star-shaped to improve the resilience and self-cleaning capacity of the roller.

3. A doctor arrangement as claimed in claim 1, wherein said means for rotating said roller are constructed and arranged so as to rotate said roller in the same direction as the drying cylinder and at a peripheral speed substantially twice that of the calender roll.

4. A doctor arrangement for cleaning the drying and calendering rolls of a paper machine which comprises in combination a rotatable roller, the axis of which is parallel to that of the calender roll to be cleaned, a pair of spaced-parallel link arms supporting said roller, said link arm-s being swingable in the axial plane of said roller, means for pressing said roller against the periphery of said calender roll, means for axially reciprocating said roller, and means for rotating said roller with a peripheral speed independent of that of said calender roll, said roller comprising a shaft, a number of annular felt discs threaded on said shaft and a number of intermediate spacing Washers between said annular discs for keeping said discs peripherally separated and spaced apart, said washers having an outer diameter smaller than that of said discs, the reciprocating stroke of said roller being larger than the total thickness of one of said discs and one of said washers.

'1 motor mounted on one of said link arms and a power H transmission including two universal joints for connecting said motor to said roller.

6. A doctor device for cleaning the calender rolls of a paper machine which comprises in combination a rotatable roller, the axis of which is parallel to that of the calender roll to be cleaned, a pair of link arms supporting said roller, said link arms being swingable in an axial plane of said roller, means for pressing said roller against the periphery of said calender roll, means for rotating said roller with a peripheral speed independent of that of said calender roll, and means for imparting an axially reciprocating movement to said roller in dependence on the rotational movement thereof, said roller having a resilient self-cleaning surface formed by spaced-parallel felt discs having their peripheries spaced apart, adapted to exercise a cleaning and polishing action on the calender roll surface when rotated.

7. A doctor device for cleaning and polishing the hard surfaces of calender rolls and the like which are mounted on shafts journaled in a frame, which comprises an auxiliary shaft rigidly mounted in said frame with its axis spaced-parallel from the axis of the calender roll, a bell crank lever pivotally mounted at either end of said auxiliary shaft, each bell crank lever having two lever arms mounted at an angle to each other and being swingable in a plane perpendicular to the axes of said shafts, the corresponding arms of the two levers being spaced-parallel and of the same length, a third shaft journaled in spherical bearings at the ends of two of said lever arms adjacent said calender roll and spaced-parallel therefrom, these lever arms being pivoted adjacent their mountings on said auxiliary shaft so that said third shaft can be oscillated in an axial plane, a doctor roll having a resilient surface mounted on said third shaft and adapted to contact and clean the surface of the calender roll, adjusting screws mounted at the ends of the other two lever arms for adjusting the pressure between the doctor roll and the calender roll, means for driving the doctor roll mounted on one of said lever arms adjacent one of the said spherical bearings, and means mounted on the spaced-parallel lever arm adjacent the other spherical bearing for oscillating the doctor roll in an axial plane while contacting the surface of the calender roll.

8. A self-cleaning doctor roll adapted to be independently rotated with its surface in contact with the surface of a calender roll while being reciprocated axially, which comprises ashaft, a plurality of spaced apart discs of resilient fibrous material threaded on said shaft, a corresponding number of intermediate washers threaded on said shaft and serving to hold said discs with their peripheries spaced apart, said washers being star-shaped and having a diameter smaller than the diameter of said discs, and means for holding said washers and discs rigidly on said shaft so they will rotate with the shaft. 

